JPH0439067B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat fixing toner for electrostatic charge development, which is used to develop an electrical latent image in electrophotography or electrostatic recording.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Many methods are known, as described in Japanese Patent No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, solvent vapor, etc. to obtain a copy.

Various methods and devices have been developed for the above-mentioned final step, which is the step of fixing the toner image on a sheet such as paper. The most common method at present is the compression heating method using a heated roller.

In the press-heating method using a hot roller, fixing is performed by passing the toner image surface of the sheet to be fixed under pressure on the surface of a hot roller whose surface is made of a material that has releasability to the toner. . In this method, the surface of the heated roller and the toner image on the fixing sheet come into contact with each other under pressure.
It has extremely good thermal efficiency when fusing a toner image onto a sheet to be fixed, allows rapid fixing, and is very effective in high-speed electrophotographic copying machines. However, in the above method, since the surface of the heat roller and the toner image contact each other under pressure in a molten state, a portion of the toner image adheres to and transfers to the surface of the fixing roller, and this is transferred again to the next sheet to be fixed. One of the essential conditions for the heated roller fixing method is to prevent toner from adhering to the surface of the heat fixing roller, which may cause a so-called offset phenomenon and stain the sheet to be fixed.

Conventionally, in order to prevent toner from adhering to the fixing roller surface, for example, the roller surface is made of a material that has excellent releasability for toner, such as silicone rubber or fluorine-based resin, and the surface is also coated with anti-offset and roller surface coatings. In order to prevent fatigue, the surface of the roller is coated with a thin film of a liquid with good mold releasability, such as silicone oil. However, although this method is extremely effective in preventing toner offset, the offset prevention liquid evaporates due to heating, giving the user an unpleasant odor, and requires a device to supply the offset prevention liquid. Therefore, there are problems such as a complicated fixing device. Therefore, it is not desirable to prevent offset by supplying an offset-preventing liquid, but rather the development of a toner with high offset resistance over a wide fixing temperature range is currently desired.

As described in Japanese Patent Publication No. 51-23354, such an offset phenomenon tends to occur when a low molecular weight resin is used. Therefore, as described in the same publication, a method for preventing the offset phenomenon by using a crosslinked resin has been proposed. The inventors of the present invention have investigated and found that simply creating a crosslinked resin is not necessarily satisfactory. In particular, when the degree of crosslinking is increased, the dispersion of pigments and the like into the binder resin deteriorates, the pigments and the like are exposed on the toner surface, the development characteristics of the toner deteriorates, and the fixing temperature also rises.

Further, in the case of magnetic toner, there are problems such as increased fixing temperature and poor offset resistance.
Although crosslinking and gelatinizing the binder resin to prevent offset is certainly effective, it has the fatal drawback that the fixing point becomes too high if sufficient offset properties are provided.

Recently, since the oil crisis, energy saving has been required in various fields, and product development in office machines is also largely moving in this direction. Pressure fixing type copiers, which can significantly reduce power consumption, have started to appear on the market, but they still do not account for the majority of users, except for low-speed, low-end machines with insufficient fixing properties and poor image quality. Not yet.

There is a strong demand for energy saving in the heat roller method, which currently dominates the heat fixing method.
There is a need for a copying machine that uses less power and has faster fusing capabilities. This means that the toner can be melted and fixed at a lower temperature, that there is no offset, and that the toner particles do not aggregate or solidify during long-term storage.
It is necessary to develop a toner with good blocking resistance.

Recently, polyester-based and epoxy-based resins have attracted attention as materials more suitable for low-temperature fixing, and in particular, several patents have been disclosed regarding toners using carboxyl group-containing polymers or polyester-based toners. According to these results and experiments conducted by the inventors, toners containing polyester resin as the main binder can certainly have a lower fixing temperature than other materials, but have a problem with offset properties. However, as seen in JP-A-56-94362, 56-116041, and 56-166651, a method was discovered to improve the offset property by adding a polyvalent metal compound to cause a type of crosslinking and gelation with the metal, and it has been put into practical use. It's getting closer to becoming a reality.

However, the reaction that imparts this crosslinking property is carried out in a state where the solids are made meltable by heating, and the opportunity for aggregation during kneading is greatly affected, and the type and amount of metal compound, reaction conditions, etc. are extremely delicate and control is extremely difficult. It has the disadvantage that it is difficult to maintain a constant dispersibility of various materials and a constant degree of crosslinking. Furthermore, relatively simple kneading machines such as extruders and kneaders that have been widely used in the production of dry toner and have a large processing capacity are insufficient, and it is highly anticipated that production costs will rise, as existing equipment will no longer be usable.

Therefore, in order to commercialize toners whose main binder resin is polyester or carboxyl group-containing polymers, which are superior in terms of low-temperature fixing, crosslinking with metals must be done not during hot kneading but when cold. It is predicted that the important point will be whether or not it is possible to do so.

In addition, to improve the offset properties, charging properties, and anti-blocking properties of the original toner, it is sufficient to modify only the surface, or to modify the necessary amount sequentially from the surface toward the core, so that the toner has already been sufficiently crosslinked and gelled. The basic technical idea of this application is that there is no need to use a special adhesive, and when we implemented it based on this idea, the results were almost as expected, with sufficient fixation at lower temperatures, good non-offset properties, and excellent blocking resistance. This method has been developed to produce a toner that has good overall characteristics, including good properties and stable chargeability.

That is, an object of the present invention is to provide a method for producing a toner for hot roller fixing which can be sufficiently fixed at a lower temperature and has good offset resistance.

A further object of the present invention is to provide a method for producing a toner with excellent blocking resistance, which does not cause development such as aggregation or caking even when left in a relatively high temperature environment for a long period of time. It is.

A further object of the present invention is to provide a method for producing a toner for hot roller fixing that has good chargeability and always shows stable chargeability during use, and provides clear and fog-free images.

A further object of the present invention is to provide a method for producing a toner for hot roller fixing that has excellent fluidity, does not cause aggregation, and has excellent impact resistance.

A further object of the present invention is to provide a method for producing a toner for thermal roller fixing that causes less deposits on the surface of a toner holding member or photoreceptor.

A further object of the present invention is to provide a method for producing a magnetic toner that, when used as a magnetic developer, exhibits good and uniform magnetism and can be fixed by a hot roller.

Specifically, the present invention provides a dry toner for heat fixing using a carboxyl group-containing resin as the main binder resin,
Al, Ba, Ca, Co, Cr, Cu, Fe, Hg, Mg,
The toner particle surface of the heat fixing dry toner is modified by immersing it in an aqueous solution of a metal salt of a divalent or higher valent metal selected from the group consisting of Mn, Ni, Pb, Su, Sr, and Zn. The present invention relates to a method for producing a dry toner for heat fixing. Although the details of the physicochemical mechanism of the present invention are unknown, a metal with a valence of more than 2 interacts with the acidic group, that is, the carboxyl group, on the surface of the toner to form a kind of metal salt, which connects the carboxyl groups with each other. causes crosslinking of
It is thought that the offset resistance is improved in the same way as when a decomposable metal compound is added. It is also believed that the adhesion of these metals to the surface improves blocking resistance.
Note that the modification effect of the metal aqueous solution was more effective with the metal salt aqueous solution of a divalent or higher valent metal than with the metal salt aqueous solution of a monovalent metal.

Various types of carboxyl group-containing polymers can be used in the present invention, such as polymers obtained by copolymerization of carboxyl group-containing vinyl monomers with other vinyl monomers, and polymers obtained by ionic polymerization of vinyl monomers by blowing carbon dioxide gas into them. Polymers obtained by partially oxidizing polymers having unsaturated double bonds in the main chain or side chains, polymers obtained by hydrolyzing polymers having ester bonds in side chains, etc. are used. be done.

Further, as the main structural unit components of the carboxyl group-containing polymer, for example, the following carboxyl group-containing vinyl monomers and other vinyl monomer components can be mentioned.

Carboxyl group-containing vinyl monomers acrylic acid, methacrylic acid, α-ethyl acrylic acid, crotonic acid, isocrotonic acid, β-methylcrotonic acid, maleic acid, fumaric acid, itaconic acid,
Vinyl acetic acid, angelic acid, tiglic acid, 4-pentenoic acid, citraconic acid, mesaconic acid, glutaconic acid, α- or β-dihydromuconic acid Other vinyl monomers Alkyl esters derived from the above unsaturated carboxylic acids, halogenated alkyl esters, Alkoxyalkyl esters, aralkyl esters, alkenylnisters, aminoalkyl esters, amides and nitriles: aliphatic monoolefins such as ethylene, propylene, butyne, isobutylene;
Vinyl chloride, vinyl bromide, vinyl iodide, 1,2
- halogenated aliphatic olefins such as dichloroethylene, 1,2-dibromoethylene, 1,2-diiodoethylene, isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride; 1,3 -butadiene, 1,3-pentadiene, 2-methyl-1,3-butadiene, 2,
Conjugated diene aliphatic diolefins such as 3-dimethyl-1,3-butadiene, 2,4-hexazinine, and 3-methyl-2,4-hexadiene; styrene, alkyl groups of styrene, halogen atoms, nitro groups, alkoxyl groups, Nuclear substitutes such as acyl groups.

In addition, the divalent or higher valent metal salt compounds used in the present invention include Al, Ba, Ca, Co, Cr, Cu, Fe, Hg,
Sulfate of Mg, Mn, Ni, Pb, Su, Sr or Zn,
Examples include nitrates, phosphates, carbonates, acetates, etc., and among these, those that dissolve well in water for use may be appropriately selected.

All known dyes and pigments can be used as the coloring material used in the toner together with the binder of the present invention, such as carbon black, iron black,
Examples include, but are not limited to, metal complex dyes, red iron, phthalocyanine blue, and chrome yellow. Further, as carriers used in toner, iron powder, nickel powder, glass beads, and those whose surfaces are treated with resin or the like are used.

Known thermoplastic resins, such as polyester resins other than the present invention, within a range that does not impair the performance of the present invention,
Urethane resin, epoxy resin, ethylene-ethyl acrylate resin, phenolic resin, styrene
Butadiene resin, xylene resin, petitral resin, etc. may be mixed or modified to be used. It is preferable that the amount of these known thermoplastic resins does not exceed 20% by weight in the toner binder.

Moreover, when the developing powder used in the present invention is used as a magnetic developing powder, magnetic powder is contained. Magnetic powders include ferromagnetic elements and alloys and compounds containing these elements, including alloys and compounds of iron such as magnetite and hematite ferrite, cobalt, nickel, manganese, and other ferromagnetic alloys. There is a known substance. The magnetic powder is preferably contained in an amount of 10 to 70% by weight, preferably 15 to 50% by weight, based on the weight of the developing powder.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but these are not intended to limit the present invention in any way. Note that all parts used are parts by weight.

Example 1 Styrene/butadiene/acrylic acid (75/20/
5) 100 parts terpolymer (average molecular weight 200,000) Magnetic material (EPT-1000 manufactured by Toda Kogyo) 60 parts Metal-containing dye 2 parts Low molecular weight polyethylene (molecular weight 3000) After mixing 2 parts and melt-kneading in a roll mill. The powder was coarsely pulverized with a hammer mill, finely pulverized with a supersonic jet mill, and fine powder and coarse powder were removed with an air classifier to obtain a powder for a developer having a size of 5 to 20 μm.

Next, add 200 ml of distilled water to a 500 ml beaker, and while stirring with a stirring machine, 30 g of zinc nitrate.
Gradually add the aforementioned toner powder after completely dissolving it.
Add 100g and soak for 10 hours while continuing to stir. Further, the processing temperature at this time needs to be within the range of 20 to 40°C. The soaking time should not be longer than necessary. After the treatment time was over, the soaked product was placed on a nuttie covered with paper under reduced pressure, and after removing the liquid, it was thoroughly washed with distilled water about 10 to 20 times the amount of the powder. This was poured into a vat, lightly crushed, and then left in a dryer at 40 to 50°C for 24 hours to obtain a dry powder.

After adding and mixing 0.3 parts of hydrophobic colloidal silica to 100 parts of this dry powder, a commercially available copying machine (manufactured by Canon)
We conducted a continuous image output test of 10,000 sheets of A3 size using the NP-200J). As a result, a very clear and good image with no background fog was obtained, and this was maintained until the end of the test.

Furthermore, after the test was completed, the fuser was disassembled and the degree of dirt on the rollers and the amount of dirt and offset material on the cleaning blade for removing offset material were examined. There were no problems whatsoever.

Also, take a small amount of the developer obtained above in a container,
After leaving it in a constant temperature bath kept at 50℃ for 24 hours, we examined the properties of the powder and found that it remained in an extremely fluid state without any problems, and there was no blocking phenomenon due to aggregation of toner particles. Nakatsuta.

Comparative Example 1 A test was conducted in the same manner as in Example 1 except for the step of immersing it in a metal salt aqueous solution, and in the continuous image output test, initially clear and good image quality was obtained. An offset image due to offset during removal and fixing appears mainly in a linear form on the copy.
I had no choice but to interrupt the test.

When the fuser was disassembled after the interruption, the rollers were smeared with toner in several places, and the cleaning blade was caked with mountains of offset toner, making it completely unusable.

In addition, the storage stability of the toner was examined in the same manner as in Example 1. After being left at 50°C for 24 hours, the toner was found to have lumps and clumps in some places, which were thought to be due to aggregation and fusion of the toner, and some of the toner could be pressed with a finger. Some of them did not disintegrate easily, and their blocking resistance was poor.

Example 2 A test was conducted in exactly the same manner as in Example 1, except that zinc sulfate was used instead of zinc nitrate as the metal salt compound, and the results were almost the same as in Example 1. It was hot.

Comparative Example 2 The same procedure as in Example 2 was carried out except for the step of immersing the toner in an aqueous metal salt solution, but the results were almost the same as in Comparative Example 1.

Example 3 In Example 1, 100 parts of styrene/butyl acrylate/monobutyl maleic acid (75/15/10) terpolymer (molecular weight 350,000) was mixed with 100 parts of styrene/butadiene/acrylic acid terpolymer. When the same procedure was carried out except for using the same method as in Example 1, the results were almost the same as those in Example 1.

Example 4 In Example 3, Zn(NO ₃ ) ₂ was used as the metal salt compound.
When the same procedure was repeated except that PbSO ₄ was used instead of PbSO 4 , excellent results were obtained as in Example 3.

Comparative Example 3 A comparison was made in exactly the same manner as in Example 1 except that styrene/butyl acrylate (75/25) 100 parts copolymer was used instead of styrene/butadiene/acrylic acid 100 parts terpolymer. Similar to Example 1, the results were poor.

Example 5 The same procedure as in Example 1 was carried out except that 100 parts of oxidized polyethylene wax and 100 parts of Mitsui Hiwax 1105A (acid value 60) were used instead of the styrene/butadiene/acrylic acid terpolymer. Almost the same excellent results as in Example 1 were obtained.

Comparative Example 4 The same procedure as in Example 5 was carried out except for the step of immersing in the metal salt aqueous solution, and the result was almost the same as that of Comparative Example 1.

Example 6 Styrene/butadiene/acrylic acid (75/20/
5) 100 parts Terpolymer average molecular weight 200,000 Metal-containing dye 2 parts Low molecular weight polyethylene (molecular weight 3000) 2 parts After mixing the above materials, knead with a roll mill, coarsely crush with a hammer mill, and then finely crush with a supersonic jet mill and average. A powder for development with a particle size of 8 μm was obtained.

Dissolve 30g of zinc nitrate in 200ml of water, add 100g of the aforementioned developing powder, soak for 10 hours, filter the liquid,
Rinse well with plenty of water and dry.

10 parts of this dry powder and carrier iron powder (trade name,
A developer was prepared by mixing 90 parts of EFV250/400 (manufactured by Nippon Tetsuko Co., Ltd.). This developer was applied to a commercially available plain paper copying machine (product name NP-5000, manufactured by Canon) and a continuous copying test of 10,000 sheets of A3 size paper was conducted.

As a result, an extremely clear image with no background fog was obtained, and this image was maintained until the end of the test.

Further, after the test was completed, the fixing device was disassembled and the degree of dirt on the rollers was examined.The rollers were found to be hardly dirty and pose no problem in practical use.

In addition, a small amount of the dry powder mentioned above was placed in a container and left in a constant temperature bath kept at 50℃ for 24 hours.The properties of the powder were then examined. No blocking phenomenon due to aggregation, adhesion, etc. was observed at all.

Comparative Example 5 A3 version 1 carried out in exactly the same manner as in Example 6 except for the step of immersing it in a zinc nitrate aqueous solution.
In the 10,000-sheet image printing test, initially very clear and high-quality images with no background fog were obtained, but later on, an offset phenomenon appeared, and an offset image appeared on the transfer paper, and the back side of the transfer paper I had no choice but to stop the test because it was so dirty.

Also, after the interruption, I disassembled the fuser and checked how dirty the rollers were, but the fuser roller, back-up roller,
Almost all of the heat supply rollers were black and dirty and in poor condition.

In addition, a small amount of the obtained developing powder (without carrier) was placed in a container and left in a constant temperature bath kept at 50°C for 24 hours, and the properties of the powder were examined.
There were clumps of adhesion scattered here and there, and some of the pieces were so hard that they wouldn't disintegrate when pressed a little with a finger, making it far from being of any practical use.

Claims (1)

[Claims] 1 Heat-fixing dry toner containing a carboxyl group-containing resin as the main binder resin is mixed with Al, Ba, Ca, Co, Cr,
Cu, Fe, Hg, Mg, Mn, Ni, Pb, Su, Sr and
A method for producing a dry toner for heat fixing, which comprises modifying the surface of toner particles of the dry toner for heat fixing by immersing the toner in an aqueous solution of a metal salt of a divalent or higher valent metal selected from the group consisting of Zn.